Η αντιπάθεια ανάμεσα στους δύο γείτονες, που μένουν στον ίδιο όροφο, δεν βοηθάει καθόλου την πολυκατοικία.

Because αντιπάθεια is the subject of the sentence, and it is a feminine singular noun.

• η = the (feminine singular)
• αντιπάθεια = dislike / hostility / antipathy

So Η αντιπάθεια means the hostility or the mutual dislike.

Even though there are two neighbors in the sentence, the main thing being talked about is the hostility between them, so the sentence begins with that noun.

This means between the two neighbors.

Breakdown:

• ανάμεσα = between
• στους = σε + τους = to/in/at the (masculine plural)
• δύο = two
• γείτονες = neighbors

So literally it is something like between at the two neighbors, but in natural Greek this is just the normal structure for between the two neighbors.

A useful pattern is:

• ανάμεσα σε κάποιον / κάποιους = between someone / some people

So here:

• ανάμεσα στους δύο γείτονες = between the two neighbors

Because ανάμεσα commonly combines with σε + accusative in Modern Greek.

Here:

• σε + τους becomes στους
• γείτονες is the plural accusative form

For γείτονας (neighbor), the plural nominative and plural accusative happen to look the same:

• nominative plural: γείτονες
• accusative plural: γείτονες

So even though the form looks the same, its role here is accusative because it follows σε.

It describes τους δύο γείτονες — the two neighbors.

So the structure is:

• οι δύο γείτονες = the two neighbors
• που μένουν στον ίδιο όροφο = who live on the same floor

This is a relative clause. It gives extra information about the neighbors.

Because που refers to δύο γείτονες, which is plural.

So the verb must also be plural:

• μένει = he/she lives
• μένουν = they live

Since there are two neighbors, Greek uses μένουν.

Here που means who or that.

It is a very common Greek relative pronoun, and unlike English relative pronouns, it does not change form for gender or number.

So:

• ο άντρας που... = the man who...
• η γυναίκα που... = the woman who...
• τα παιδιά που... = the children who...

In this sentence:

• οι δύο γείτονες, που μένουν... = the two neighbors, who live...

Because this relative clause is giving extra, non-essential information.

The sentence already identifies the people as the two neighbors. The part που μένουν στον ίδιο όροφο just adds more detail about them.

This is similar to English:

• The hostility between the two neighbors, who live on the same floor, ...

The commas show that this is not defining which neighbors, but simply adding information about them.

This means on the same floor.

Breakdown:

• στον = σε + τον
• ίδιο = same
• όροφο = floor

So:

• στον ίδιο όροφο = on the same floor

ίδιος / ίδια / ίδιο behaves like an adjective and agrees with the noun:

• ο ίδιος όροφος (nominative)
• στον ίδιο όροφο (after σε, accusative form)

Because the idea is that both neighbors live on the same one floor, not on several floors.

So Greek uses the singular:

• στον ίδιο όροφο = on the same floor

If they lived on different floors, the sentence would be different.

Because the subject of the sentence is not the two neighbors. The subject is Η αντιπάθεια.

So the grammar is:

• Η αντιπάθεια ... δεν βοηθάει ...

Since αντιπάθεια is singular, the verb is singular too:

• βοηθάει = helps

The two neighbors are inside the phrase ανάμεσα στους δύο γείτονες, which tells us where the hostility exists, but they are not the grammatical subject.

Both are correct in Modern Greek.

• βοηθά
• βοηθάει

These are two common present-tense forms of the same verb. In many contexts, they are interchangeable.

So:

• δεν βοηθά καθόλου
• δεν βοηθάει καθόλου

Both mean doesn’t help at all.

καθόλου means at all or not at all.

With negation (δεν), it strengthens the idea:

• δεν βοηθάει = it doesn’t help
• δεν βοηθάει καθόλου = it doesn’t help at all

So it makes the statement more emphatic.

Because πολυκατοικία is the direct object of βοηθάει.

• η πολυκατοικία = the apartment building / block of flats
• την πολυκατοικία = the apartment building (accusative)

The verb βοηθάω / βοηθώ takes a direct object, so Greek uses the accusative here.

It can suggest both, depending on context.

Literally, πολυκατοικία is an apartment building / block of flats. But in a sentence like this, it often implies the wider life of the building as well — the shared environment, relationships, and general atmosphere among the residents.

So δεν βοηθάει καθόλου την πολυκατοικία is not only about the physical building; it means the hostility is bad for the building as a living community.

Yes, Greek word order is more flexible than English word order, though this version sounds natural and clear.

This sentence puts the emphasis first on:

• Η αντιπάθεια = the hostility

That makes sense because it is the main topic.

A different order is sometimes possible, but Greek often prefers to place the subject early when introducing the main point.

A simple way to see it is:

• Η αντιπάθεια = subject
• ανάμεσα στους δύο γείτονες = phrase explaining where / between whom
• που μένουν στον ίδιο όροφο = relative clause describing the neighbors
• δεν βοηθάει καθόλου = verb phrase
• την πολυκατοικία = direct object

So the core sentence is:

• Η αντιπάθεια δεν βοηθάει καθόλου την πολυκατοικία.

And the middle part adds detail:

• ανάμεσα στους δύο γείτονες, που μένουν στον ίδιο όροφο,

That is why the sentence may look long, but its main grammar is actually quite straightforward.